The placenta is a key organ during pregnancy that is rich in blood vessels, which facilitate nutrient uptake, waste elimination, and gas exchange. Due to the presence of the developing fetus and the fact that human placenta is very different from nearly all other animal placenta, many of the current imaging technologies that would provide the necessary resolution to visualize human placenta structure and function cannot be utilized in vivo. Ultrasound imaging is nearly alone in its capability to safely image human placenta; however current ultrasound imaging technology cannot adequately visualize the vessels supplying and traversing this organ during its developmental phase. Novel tools to visualize and study the vascular network would be useful for understanding normal and abnormal placental development, including common placenta disorders such as preeclampsia and intrauterine growth restriction. In this application, we propose to develop a new ultrasonic imaging method for flow detection, called Coherent Flow Power Doppler (CFPD) that greatly enhances the ability to visualize small vessels with slow blood flow. We present preliminary data demonstrating the success of this technique in simulations, phantoms, and off-line in vivo data. We also propose to build this imaging system onto a clinical scanner, for high-quality real-time imaging of the in viv placenta. We propose to analyze the real-time CFPD imaging system in a clinical study involving the maternal spiral arteries, which are key vessels in the placenta development process and are linked to placental disorders such as preeclampsia and intrauterine growth restriction.